Wavelength-division multiplexing (WDM) may be used to increase communication bandwidth by sending multiple data channels operating at different wavelengths down a single waveguide, such as an optical fiber. A multiplexer is used to join the signals together before transmission, and a demultiplexer is used to separate a received signal into constituent signals.
Throughout the drawings, a hyphenated index number “N” appended to some of the reference numerals may be understood to merely denote plurality. Additionally, use herein of a reference numeral without a hyphenated index number, where such reference numeral is referred to elsewhere with a hyphenated index number, may be a general reference to the corresponding plural elements, collectively or individually.